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Pulmonary hypertension

Introduction

Pulmonary hypertension is high blood pressure in the blood vessels that supply the lungs (pulmonary arteries).

It's a serious condition that can damage the right side of the heart.

The walls of the pulmonary arteries become thick and stiff, and can't expand as well to allow blood through. The reduced blood flow makes it harder for the right-hand side of the heart to pump blood through the arteries.

If the right-hand side of your heart has to continually work harder, it can gradually become weaker. This can lead to heart failure.

Pulmonary hypertension is a rare condition that can affect people of all ages, but it's more common in people who have another heart or lung condition.

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Causes of pulmonary hypertension

Pulmonary hypertension is caused by changes to the pulmonary arteries, which are blood vessels that carry blood from your heart to your lungs.

The walls of your pulmonary arteries can become stiff and thickened, or the blood vessels may get blocked by blood clots. This makes it difficult for your heart to pump blood through these arteries, increasing pressure inside them and leading to pulmonary hypertension.

There can be many different reasons for the changes to your arteries. The World Health Organization (WHO) has classified pulmonary hypertension into five different types, depending on the underlying cause. They are:

pulmonary arterial hypertension (PAH)

pulmonary hypertension associated with left heart disease

pulmonary hypertension associated with lung disease and hypoxia

pulmonary hypertension due to blood clots

pulmonary hypertension due to other causes

These are described below.

Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is caused by problems with the smaller branches of the pulmonary arteries. In PAH, these changes are usually the main problem, rather than another condition.

As the pulmonary arteries are directly affected, they can be treated immediately, whereas in other types of pulmonary hypertension, the underlying cause must be treated first.

PAH can be further divided into specific subtypes, which are described below.

Idiopathic PAH

Idiopathic means that the cause is unknown. If tests cannot find an underlying reason for your condition, you may be diagnosed with idiopathic PAH. This is an extremely rare condition, only affecting around two people in every million each year.

Inherited PAH

Some cases of PAH run in families. A particular genetic mutation (a change in one of the genes you inherit from your parents) is sometimes thought to cause PAH. There may be a family history of the condition in up to 10% of idiopathic PAH cases.

PAH associated with other conditions

Other conditions or treatments associated with PAH include:

connective tissue diseases that affect the structure or composition of your body tissue – such as scleroderma (a disorder that causes hardening of the skin)

meconium aspiration syndrome– where a newborn baby breathes in a mixture of amniotic fluid (the fluid that surrounds the baby in the womb) and meconium (their first faeces), which can block their airways

Left heart disease

Pulmonary hypertension is sometimes associated with diseases that affect the left side of the heart (the side that pumps blood around the whole body, apart from the lungs). The left side of the heart consists of:

the left atria (upper chamber)

the left ventricle (lower chamber)

the aortic and mitral valves – one-way valves that allow blood to flow through the heart in the correct direction

As blood flows through the pulmonary arteries to the lungs and then to the left side of the heart, any problem could have a backwards effect on this circuit and affect the pulmonary arteries. This in turn could cause pulmonary hypertension.

Up to 60% of people with a condition that causes severe left ventricle dysfunction have pulmonary hypertension. Almost all people with a severe mitral valve condition, and nearly two-thirds of those with a severe aortic valve condition, have pulmonary hypertension.

Lung disease and hypoxia

Pulmonary hypertension is also sometimes associated with lung diseases or hypoxia (a shortage of oxygen in the body). This includes:

chronic obstructive pulmonary disease (COPD)– a term that describes a number of lung diseases that affect breathing; up to half of people with advanced COPD may also have pulmonary hypertension, although it's usually mild

interstitial lung disease– a group of lung disorders that cause scarring of the lung tissue, which makes it difficult to get enough oxygen into your body; about a third of people with interstitial lung disease may have pulmonary hypertension

These types of conditions can restrict the amount of oxygen able to get into your lungs and enter your blood. A low level of oxygen in the blood causes the pulmonary arteries to constrict (get narrower). As these vessels are narrower, the blood is squeezed into a smaller space, which increases the blood pressure and results in pulmonary hypertension.

Blood clots

Pulmonary hypertension is sometimes the result of a blood clot that causes narrowing or a blockage in the pulmonary arteries or veins.

A blood clot that blocks one of the blood vessels that supply your lungs is known as a pulmonary embolism.

Other causes

Other, less common, causes of pulmonary hypertension include:

sarcoidosis– a condition that causes inflammation of different organs, including the lungs and lymph nodes

histiocytosis X– a rare condition that causes scarring (granulomas) and air-filled cysts, predominantly in the lungs

compression of the blood vessels in the lungs– for example, due to a tumour

Diagnosing pulmonary hypertension

Pulmonary hypertension can be difficult to diagnose, because symptoms are often similar to other conditions that affect the heart or lungs.

This means there can sometimes be a long delay before a correct diagnosis is made.

However, as pulmonary hypertension can be serious, it's important that you visit your GP if you have symptoms, such as breathlessness and fatigue (extreme tiredness). Your GP will ask about:

your symptoms and how they affect your life

your family history (some types of pulmonary arterial hypertension may run in families)

whether you are currently taking any medication

whether you have any other medical conditions

Your GP may also perform a physical examination, to check for leg or ankle swelling, and listen to your heart and lungs with a stethoscope.

Testing

You may have several tests, either to diagnose pulmonary hypertension, or to identify an underlying condition that may be causing it. The initial tests, described below, may be carried out by your GP or a hospital specialist.

Echocardiogram

An echocardiogram is a type of scan that can determine how well your heart is working.

It uses high-frequency sound waves to create an image of an area inside your body, such as your heart. The image can be used to estimate the pressure in your pulmonary arteries.

Chest X-ray

An X-ray is an imaging technique that uses high-energy radiation to highlight abnormalities in bones and other types of tissue.

A chest X-ray can look for other causes of your symptoms, such as scarring in your lungs, which can also cause shortness of breath.

A chest X-ray can also check whether your heart is larger than normal. Pulmonary hypertension makes the right-hand side of your heart work harder, causing it to become enlarged.

Lung function tests

Lung function tests, also known as breathing tests, assess how well your lungs work.

The tests measure how quickly you are able to move air in and out of your lungs, how much air they can hold, and how well they transfer oxygen into your blood and remove carbon dioxide from it.

During the tests, you will be asked to breathe into a lung function machine. The data collected will help diagnose any underlying lung conditions.

Exercise tests

Exercise tests involve carrying out some form of exercise while checking your symptoms.

For example, you may be asked to walk on a treadmill or up and down a corridor for six minutes while your heart rate, blood pressure and oxygen levels are monitored. This can help to determine whether there are any underlying causes of your symptoms.

Ventilation-perfusion scan

A ventilation-perfusion scan measures the amount of air and the blood flow in your lungs. This can be used to look for blood clots in your blood vessels that may be causing pulmonary hypertension.

Blood tests

A sample of blood may be taken and tested to rule out other possible conditions, such as thyroid and liver disease.

Confirming the diagnosis

The above tests may suggest that pulmonary hypertension is present, but the diagnosis can only be confirmed by measuring your blood pressure in:

the right ventricle (lower chamber) of your heart – which pumps blood to your lungs

your pulmonary arteries – which carry blood from the right side of your heart to your lungs

Your blood pressure is measured using a procedure called right-heart catheterisation.

Right-heart catheterisation

In right-heart catheterisation, a thin flexible tube called a catheter is inserted into a vein in your neck, arm or groin. The catheter is then fed through into the right side of your heart and into your pulmonary arteries.

As well as measuring blood pressure, the catheter can be used to measure the:

amount of blood the right-hand side of your heart is pumping out to your lungs

pressure your heart must work against to get blood to your lungs (pulmonary vascular resistance)

Classifying pulmonary hypertension

As part of your diagnosis, your condition will be classified depending on its severity. This will help to determine the best treatment for you.

Pulmonary hypertension is classified into four types, where:

ordinary physical activities do not cause any symptoms

ordinary physical activities cause symptoms, such as chest pain or fatigue, but you have no symptoms when resting

even slight physical activities, such as moving your arms, cause symptoms, but you have no symptoms when resting

you have symptoms when resting, which are increased with any type of physical activity

Newborn babies

Newborn babies can have a type of pulmonary hypertension called persistent pulmonary hypertension of the newborn.

This can be diagnosed using some of the same tests used for adults, such as an echocardiogram and right-heart catheterisation.

Treating pulmonary hypertension

If you have pulmonary hypertension caused by another underlying condition, your treatment will focus on tackling it.

If the cause is identified and treated early, it may be possible to prevent permanent damage to your pulmonary arteries (the blood vessels that supply your lungs).

If you have pulmonary arterial hypertension (PAH), you will be referred to a centre that specialises in treating this form of the condition. There are seven centres in England and one in Scotland. They are:

Diuretics

Diuretics are used to remove excess fluid from the body by increasing the production and flow of urine.

In pulmonary hypertension, diuretics may be used to treat fluid retention and swelling (oedema). This can occur if the condition starts to cause heart failure, where your heart struggles to pump blood around your body.

Diuretics used include:

furosemide

amiloride

spironolactone

Diuretics can cause side effects such as:

mild tummy upset

postural hypotension– where your blood pressure drops suddenly after moving, which can make you feel dizzy after you stand up

Diuretics can also disrupt your levels of electrolytes (minerals in your blood, such as potassium) and affect your kidney function. Because of this, your kidneys and blood will be monitored while you are taking diuretics.

Oxygen

If you have low oxygen levels in your blood, you may need to be treated with oxygen. This involves inhaling air that contains a higher concentration of oxygen than normal. This will increase the amount of oxygen in your blood and should help to improve your symptoms.

Nifedipine and diltiazem are two possible calcium channel blockers that may be prescribed.

Calcium channel blockers may work for people with idiopathic PAH (where there is no known cause). However, the effect in other types of PAH is less clear.

You will need a vasoreactivity test to find whether calcium channel blockers are suitable for you. This involves taking the medication and then checking whether the blood pressure in your pulmonary arteries has fallen. If it has, you may be prescribed calcium channel blockers.

If calcium channel blockers are not suitable for you, or are no longer effective, further treatments can be used. These are called targeted therapies and include the following medicines:

bosentan

ambrisentan

macitentan

sildenafil

tadalafil

iloprost

veletri

epoprostenol

riociguat

Some of these are described below.

Bosentan

Bosentan tablets may help to improve your symptoms and ability to exercise. Two tablets are usually taken twice a day (in the morning and evening), although the dosage can sometimes vary.

You may need to spend a day in hospital when you start treatment. If your condition has not improved after 8-16 weeks, or if it has got worse, you may be given additional treatment as well as, or instead of, bosentan.

Bosentan can increase levels of some enzymes in the liver, which can cause liver damage. It may also cause anaemia in some people. As a result, your liver will need to be monitored once a month for as long as you are taking bosentan.

Fluid retention – for example, leg swelling – has been reported in up to 30% of patients using bosentan.

Ambrisentan and macitentan

These act in similar ways to bosentan, but only need to be taken once a day. The side effects are also similar, and monthly blood tests will be required to exclude liver abnormalities and anaemia.

Sildenafil

Sildenafil tablets are usually taken three times a day to improve your ability to exercise.

You may need to spend a day in hospital when you start treatment, before returning home and carrying on taking the medicine. How long you can take sildenafil for will depend on your condition. If at any time your condition gets worse, you may be given additional treatment as well as, or instead of, sildenafil.

Sildenafil may not be suitable for you if you:

are also taking medicines or drugs that contain nitrates – organic nitrates are often used to treat angina and amyl nitrate is a recreational drug commonly known as "poppers"

Tadalafil

Tadalafil acts in exactly the same as sildenafil, but only needs to be taken once a day. Its side effects are also similar to sildenafil.

Iloprost

Iloprost is inhaled through a nebuliser. This is a device that turns the liquid medicine into a mist you breathe in to your lungs. You may need to take iloprost six to nine times a day. Each dose can take up to 10 minutes to inhale.

You will need to stay in hospital for up to three days, so that you can be trained in using the nebuliser, and to monitor your response. After this, you should be able to return home and continue taking the medicine.

How long you need to take iloprost for will depend on your condition. You may need to continue taking it, possibly alongside other treatments, until your condition worsens and you need epoprostenol (see below).

your pulmonary hypertension is caused by pulmonary veno-occlusive disease (a rare condition that causes high blood pressure in the lungs)

your pulmonary hypertension is unstable, with advanced right heart failure

Epoprostenol

Epoprostenol (full name: epoprostenol sodium) may be used if you do not respond to other treatments or if your condition is severe.

Epoprostenol needs to be given through an intravenous infusion, where a constant drip of medicine passes through a narrow tube into a vein in your arm or chest.

Treatment with epoprostenol will begin in hospital. It may take one to two weeks to find the correct dose for you. After this time it is possible, with special training and equipment, for you or your carer to learn how to administer the medicine yourself at home.

Once you have started taking epoprostenol, you may not be able to stop. Coming off epoprostenol may cause your pulmonary hypertension to rapidly return, so you may need to take the medication for the rest of your life. This is why epoprostenol is considered last, after other treatments have not worked or your condition has got worse.

Epoprostenol may not be suitable for you if you have heart failure caused by a problem with the left side of your heart, or if you have or develop pulmonary oedema (fluid on the lungs).

Lung or heart-lung transplant

A transplant may be an option in cases of severe pulmonary hypertension. It is a major surgical procedure that involves transplanting healthy lungs or a heart and lungs from a donor into a recipient.

However, less than 200 lung and heart-lung transplants are carried out each year in the UK, due to a shortage of donors.